Cryogenic cooling apparatuses for cooling radiation detectors to cryogenic temperatures are well known and widely used. In certain implementations, such a radiation detector is employed with an electron microscope for detecting X-rays incident on a specimen being spectroscopically examined. The specimen is placed within the microscope and receives incident X-ray radiation from the microscope. The scattered radiation from the specimen is then detected by a cryogenically cooled detector which converts the radiation to an electrical signal in a known way for spectroscopic analysis. The detector is mounted on an elongated structure referred to in the art as a cold finger. The finger is cantilevered to a support so as to be placed within the region of the electron microscope adjacent to the specimen. The interior of the microscope and the region surrounding the cold finger are within an evacuated chamber. Cooling of the detector is accomplished by the finger which is thermally conductively connected to a source of cryogenic cooling, for example, a Dewar containing liquid nitrogen.
U.S. Pat. No. 4,910,399 discloses an electron microscope with an X-ray detector in an arrangement as described above. U.S. Pat. No. 3,864,570 also disclose an X-ray detector for use with an electron beam producing device disclosing a cold finger structure. British Patent 2,192,091 discloses a still further embodiment of an electron microscope and X-ray detector system of the type described.
Typically in these kinds of systems, it is to reduce heat input to the cold finger mounting the X-ray detector by using low emissivity warm surfaces and by wrapping the cold finger with low emissivity aluminized mylar. One hundred percent of the heat input to the system is radiated to the mylar and then conducted to the cold finger or conducted through the supports directly to the cold finger. The cold finger conducts 100% of the heat input along its length to the heat sink comprising the Dewar. This results in a large difference in temperature between the heat sink and the end of the cold finger supporting the detector and results in an undesirable high detector temperature. Additionally, the mylar and other organic compounds used in the insulation system in the evacuated chamber in which the cold finger is secured evolve contaminants undesirable when used in a UHV environment.